The inflammatory response is characterized by the accumulation of extracellular matrix (ECM) proteins at sites of injury and infection. Mast cells and basophils play an important role in the inflammatory response by releasing an array of mediators. Both cells have receptors, i.e. integrins, that can mediate binding to the ECM. Using the mast cell line, rat basophilic leukemia (RBL-2H3) cells, we have observed that the interaction with the ECM regulates secretion from these cells. Furthermore, such adhesion modulated Fc_RI- mediated signal transduction in these cells. During the last year emphasis has been on the use of molecular biology techniques to study the intracellular mechanisms by which integrins regulate cell function.